The present invention relates to a communication method and system and, more particularly, to a transmitter, a receiver, and a tire pressure monitoring system that can increase the integrity of transmitted information.
A vehicle may be provided with a tire pressure monitoring system (TPMS) that monitors the tire air pressure. When the vehicle is traveling, the tire pressure monitoring system monitors the tires for air pressure and temperature abnormalities by performing wireless communication with a tire valve, which is arranged on each tire and obtains the air pressure and temperature of the tire.
Each tire valve of the tire pressure monitoring system transmits a wireless signal including detection information, such as the air pressure and the temperature, and an ID code, which is checked by the vehicle. An error detection code is added to the wireless signal for bit error detection (refer to, for example, Japanese Laid-Open Patent Publication No. 2006-306202).
A wireless signal provided with the error detection code may include a large number of bit errors. Under an adverse communication environment in such a situation, the error detection code may erroneously be determined as being normal for one reason or another. To avoid such an erroneous determination, in a wireless signal, redundant information is added to the payload of the data string in addition to the error detection code. More specifically, plural pieces of identical detection information are included in a wireless signal as the redundant information. After receiving the wireless signal, the vehicle checks for errors using the error detection code. Further, the vehicle determines that there are no errors when the plural pieces of detection information are identical.
When increasing the redundant information in the wireless signal to increase redundancy, the data string of the wireless signal is elongated. This increases the amount of the transmission data. It is desirable that such increase in the amount of transmission data be suppressed, while increasing the integrity of the transmitted information. This is not limited to a tire pressure monitoring system and also applies to any system that performs wireless communication.
Accordingly, it is an object of the present invention to provide a communication method, communication system, transmitter, receiver, and tire pressure monitoring system that suppress an increase in the amount of transmission data, while increasing the integrity of the transmitted information.